1. Field of the Invention
The present invention relates to a keypad printed circuit board (PCB) assembly for a mobile phone, and more particularly to a keypad PCB assembly for a mobile phone integrated with a light guide plate providing a light-emitting function using a light emitting diode (LED) and the light guide plate.
2. Description of Prior Art
As generally known in the art, a light-emitting device of a keypad for a mobile phone is mainly a light-emitting diode (LED) type, but recently, there has been a trend towards distributing an electroluminescence (EL) type in high-cost models.
The LED type is a type in which LEDs are surface-mounted to many positions (e.g., 10 to 20 points) on a keypad to illuminate the whole of the keypad. Such an LED type has problems in that due to using so many LEDs, high power consumption is caused to shorten the lifetime of a battery, and in view of light-emitting, a difference in luminance occurs depending upon near-far effect from the LEDs, causing inhomogeneity in light-emitting.
The EL type is realized as an EL sheet having high power saving, super thinning, and homogeneous light-emitting features, and is thus spotlighted. However, the EL type has problems in that noises occur due to electrical interference, and it needs a high cost driving circuit, thereby increasing production costs.
Further, while there is an attempt to improve the quality of light-emitting by adapting a light guide plate for back light to a mobile phone, there is not yet proposed a practical method of manufacturing a light-emitting assembly to solve the above problems as well as to satisfy the objective light-emitting feature and easy productivity.